Vacuum tube seal



W. A. ROOVERS VACUUM TUBE SEAL Filed July 121, 1946 Sept. 12, 1950 Patented VACUUM TUBE SEAL Willielmlls Antonius semi-s, Eindhoven, Netherlands, assilnor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 12, 1946, Serial No. 683,084 In the Netherlands August 18, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires August 18, 1963 3 Claims.

The invention relates to a method of exhaustins and sealing a vessel whose wall consists, at least partly,.of metal, for example, an electric discharge tube with a metal base. The invention relates furthermore to vessels manufactured in accordance with this method.

In one method of manufacturing a discharge tube whose wall consists, at least party, ofmetal,

which method has been described in an earlier,

patent specification which has not yet been published, the tube is exhausted through an opening in the metal portion, whereupon a metal obturating member, for example a plate are conical stopper, is introduced in the vacuum conduit into the opening in which it is hermetically fixed. This airtight fixation is obtained, for example, by heating some solder present on the obturating member or around the opening or at both points by means of an electric current and by thus meltin: it.

This method has the drawback that it requires a separate obturating member which has to be introduced into the vacuum conduit anew for every tube, the whole operation becoming thus rather complicated.

This drawback is obviated by utilizing the method according to the present invention, In this method of exhausting and sealing a vessel whose wall consists, at least partly, of metal, the

exhaustion takes place through an opening which is provided in the metal portion and whose wall consists of a fusible obturatingsubstance, for example tin-solder, which, subsequent to the exhaustion, is caused to melt and thus stops the said opening. The obturating substance is melted by an electric current which is set up in a circuit which is closed-by pressing a movable metal body which is present in the vacuum conduit and which is connected to one of the terminals of a source of voltage, against a wall portion located in the neighbourhood of the exhaustion opening or against the fusible obturating substance itself.

which is connected to the other terminal of the sel is an electric discharge tube which is provided with a metal finding lug or exhaust tube, it is. very advantageous to provide the exhaustion opening at the end thereof. The opening itself must not be too large since otherwise it would be diilicult to stop it up. All this is carried out, for example, in such manner that at first the exhaustion opening is completely filled with the obturating substance whereupon a hole is drilled into the lump thus obtained, which hole is just large enough to ensure proper exhaustion of the vessel. After the exhaustion the small hole in the lump is easily stopped-up by the molten material. For-the purpose of facilitating the formation of a lump of obturating material, the finding lug or exhaust tube may be provided at its end remote from the tube with a conical depression extending towards the tube, The exhaustion opening is provided in this case in the vertex of this cone and this vertex itself can be easily filled-up with the obturating substance.

The invention will be explained more fully with reference to the accompanying drawings in which Fig. 1 shows in vertical section a metal tube, a metal finding lug associated with the tube, and apparatus for exhausting and sealing the tube;

and Fig. 2 shows an enlarged vertical section of a conical space is produced, which is filled-up with a quantity 3 of obturating material, as is clearly shown in enlarged section in Fig. 2. The obturating material may be for example tinsolder. Into the material 3 there is drilled a small opening 2 through which the interior of the tube 9 part of which is formed by the finding lug, can be exhausted by means of exhaustion chamber 6. Subsequent to the exhaustion of the tube 9, the

portion 5 of a body 4 present in the vacuum conduit, which portion consists, for example, of tungsten, is pressed against the bottom of the finding lug I, owing to which a circuit is closed whose terminals are connected to the finding lug I or the metal tube and to the body 1 respectively. The resiliently mounted body 4 is raised by means of a core and magnet coil 8. This source of current may be formed, for example, by a condenser charged to a high voltage. It is also possible to utilize another source of alternating or directcurrent voltage. When the circuit is closed, the heating current is supplied by means of lead-in wires at It and I l to fuse the solder 3. The solder is heated to such an extent that it melts, the

3 opening 2 being completely stopped up by the molten material. Fig. 2 shows the metal finding lug of the tube in enlarged cross section. Numeral I again denotes the metal wall of the finding lug and the opening I, in the obturating material 3, is clearly shown.

What I claim is:

1. A method of exhausting and sealing a vessel having a metal wall portion with an exhaust port therein, comprising the steps of completely obstructing said port by fusing with the walls thereof a fusible metal, forming an exhaust opening communicating with said port in said fusible metal, exhausting said vessel through said opening, bringing into contact with said portion of said exhausted vessel at said opening a metal member, connecting a source of voltage to said member and to said portion and passing an electrical heating current through said portion to heat said fusible substance to the melting point thereof, closing said exhaust opening with the melted fusible substance, and cooling said melted fusible substance to its solid state to seal said exhausted vessel.

2. A method 01' exhausting and sealing a vessel having a metal wall portion with an exhaust port therein, and an electrically conducting fusible substance in and partially obstructing said port and having a lower melting point than the surrounding metal wall portion, comprising the steps of exhausting said vessel through the partially obstructed port, bringing into contact with said fusible substance an electric contact member, and passing an electric current through said contact member, said fusible substance, and aid metal wall portion, to heat said fusible substance to the melting point thereof, closing said partially obstructed port with the so melted fusible substance, and thereafter cooling said substance to its solid state to seal said exhausted vessel.

3. A method of exhausting and sealing a vessel having a metal wall portion with an exhaust port therein, and an electrically conducting fusible metal in and partially obstructing said port and having a lower melting point than the surrounding metal wall portion, comprising the steps of exhausting said vessel through the partially obstructed port, bringing into contact with said fusible metal an electric contact member, and passing an electric current through said contact member, said fusible metal, and said metal wall portion, to heat said fusible metal to the melting point thereof, closing said partially obstructed port with the so melted fusible metal and thereafter cooling said metal to its solid state to seal said exhausted vessel.

WILHELMUS ANTONIUS ROOVERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,820,553 Berthold et al Aug. 25, 1931 2,124,428 Nolte July 19, 1938 2,125,316 Ronci Aug. 2, 1938 2,174,682 Beggs Oct. 3, 1939 2,221,868 Geiger et al Nov. 19, 1940 2,269,840 Anderson Jan. 13, 1942 

